Greg, wood/plastic composite is typically an extruded the...

Greg, wood/plastic composite is typically an extruded thermoplastic (PolyVinylChloride, PolyPropelene, PolyEthylene) with wood flour or fiber mixed in as a filler. Since it is a composite and the formulas vary widely in the mixture, the mechanical properties are very specific to a particular brand/product. You would surely need to create the material your self.